1. Field of the Invention
The present invention relates to detection of the occurrence of an axis displacement in a horizontal direction in a radar mounted on a vehicle, determination of the amount of the axis displacement in the horizontal direction, and correction of the axis displacement in the horizontal direction.
2. Description of the Related Art
A certain type of automotive radar is capable of detecting, in addition to the distance R to a target and the relative velocity V of the target, the lateral position X of the target by electronically or mechanically scanning the radiowave projection direction and thereby detecting the azimuth angle xcex8 of the target, the lateral position X being determined by solving the equation X=Rxc2x7sin xcex8. By detecting the lateral position X, it becomes possible to control vehicle-to-vehicle distance based on the distance and relative velocity of a vehicle traveling ahead of the radar-equipped vehicle.
After such an automotive radar has been installed in a vehicle, if the radar axis is displaced in a horizontal direction by an external force exerted for some reason, a displacement will occur in the azimuth angle xcex8 of the target, resulting in erroneous recognition of a target, the distance to which is being controlled.
It is an object of the present invention to provide an apparatus capable of detecting the occurrence of an axis displacement in a horizontal direction in a radar mounted on a vehicle, an apparatus capable of determining the amount of the axis displacement in the horizontal direction, and an apparatus capable of correcting the axis displacement in the horizontal direction.
An apparatus for detecting the occurrence of an axis displacement in a horizontal direction in a radar mounted on a vehicle, according to the present invention comprises: means for measuring the frequency with which vehicle-to-vehicle distance control, being performed using the radar, is released or re-set; and means for determining that the axis of the radar is displaced in the horizontal direction when the measured control release or re-set frequency is higher than a predetermined threshold.
An apparatus for determining the amount of an axis displacement in a horizontal direction in a radar mounted on a vehicle, according to the present invention, comprises: means for recognizing that a target detected by the radar is a stationary target; and means for determining the amount of the axis displacement in the horizontal direction, based on the locus of the target recognized as being a stationary target.
An apparatus for correcting an axis displacement in a horizontal direction in a radar mounted on a vehicle, according to the present invention, comprises: means for recognizing that a target detected by the radar is a stationary target; means for determining the amount of the axis displacement in the horizontal direction, based on the locus of the target recognized as being a stationary target; and means for correcting azimuth angle of the target by using the determined amount of the axis displacement in the horizontal direction.